The scene in question is right after Vader told Lando to take the princess and the Wookiee to his ship. Lando then tries to argue, with Vader telling him he's altering the deal "...and pray I don't alter it any further". (Great line hehe bad Vader). Notice how Lando touches himself (neheh) in this scene. Then answer the question

I just checked out the scene. It's too hard to see if he goes for his neck. That darn carbon chamber. It's too dark in there. But I do believe it was a possibility. Although Lando didn't go for his throat very quickly. He puts his hand up there very slowly.

If that scene was truely meant for Lando to grab his throat because of Vader, I do wish he would of went for it a little quicker. That way it would look a little more obvious. Also since the scene is a little dark, it is hard to see if he really grabs his throat, or he just puts his hand near it. Things that make you think.

Obviously, none of you guys are aware that Lando was very strong in the Force.

It just so happened that, at that particular moment, he was experiencing a "future event" where he was being choked by a walking carpet.

Guys, Vader's "Force choke" is his signature calling card (or notice of eviction?). I'm sure most of the Empire is aware of his predilication for suffocation. It was an unconcious move on Lando's part, based on what Vader is known to do (kinda like grabbing your balls after a near miss -- you can just imagine what it would have felt like.)

According to the novel, Vader gave Lando a warning by giving him a slight choke. I know that there are some inconsistencies between the books and the films, but there's nothing that can disprove the fact that Vader meant business when Lando tried to defy him.

Yeah, that never really registered with me until I read someone suggest it here a while back. Looking at it now, it's a pretty subtle, cool scene. Lando grabs his throat with a "wait, did HE just do that?" look.